In recent years, there has been an increased number of vehicles in which an operation input is performed by touching a menu item (e.g., command button) displayed on a screen of a display (e.g., a monitor of a navigation apparatus). Such an operation input method is employed in a system disclosed in JP-2006-309511A. In another system disclosed in US 2005/0068296 corresponding to JP-2005-100151A, a display is located at the front of a vehicle interior to reduce a movement of a driver's line of sight. However, since the display is located at a distance from a driver, it is hard for the driver to touch a menu item displayed on a screen of the display. Therefore, the system includes a remote control apparatus having an operation input device installed in a center console of a vehicle. The remote control apparatus causes a pointer to move on the screen according to operation of the operation input device so that the menu item can be selected by the pointer.
There is a possibility that the pointer may become out of control due to a fault in the operation input device. Therefore, it is preferable that the remote control apparatus have a fault diagnostic function to diagnose a fault in the operation input device. JP-2003-252027A discloses an electronic apparatus having a diagnostic function. The electronic apparatus includes a built-in display, and a fault condition can be displayed on the built-in display.
It is assumed that a diagnostic function as disclosed in JP-2003-252027A is added to a remote control apparatus as disclosed in US 2005/0068296. In such a case, a communication circuit is required to display a fault condition on a screen of a display, because the display is separated from an operation input device. Therefore, if communication is not established due to a fault in the communication circuit, the fault condition cannot be displayed on the screen. Further, if a communication error occurs due to the fault in the communication circuit, the fault condition displayed on the screen may incorrectly indicate that a fault occurs in the operation input device, not in the communication circuit.